In an optical waveguide using a photo-curable resin such as plastic, in contrast to an optical waveguide using another material, deformation of a core portion and a clad portion or fracture of the core portion due to temperature change do not occur because it is cured when exposed to light. Further, because the optical waveguide is made of a photo-curable resin, it offers an advantage in that a complicated optical waveguide can be formed easily with use of a process. Thus, application to a low-cost and high-performance optical waveguide element is anticipated and examined.
FIGS. 4A to 4C show a method of manufacturing an optical waveguide according to a related art. First, a lower substrate 93 in which a lower clad layer 92 is laminated on a lower base film 91 is prepared. A core 94 is placed on the lower substrate 93. Further, an upper substrate 97 in which a curable resin layer 96 is laminated on an upper base film 95 is prepared. Then, the upper substrate 97 is pressed on top of the lower substrate 93. At this time, the curable resin layer 96 is deformed into a shape surrounding the core 94 because it is flexible.
After that, by exposure to light, the curable resin layer 96 changes into a clad layer 98. An optical waveguide device 90 in which the clad layers 92 and 98 are formed so as to surround the core 94 is thereby fabricated (e.g. Patent Document 1).
[Patent Document 1]
    Japanese Unexamined Patent Application Publication No. 2005-115047